You are right about open source developers who do this on the side, as a hobby, and even if they don't are usually underpaid and understaffed. They do deserve more time and a different approach.
But corporations making big bucks from their software need to be able to fix things quickly. They took money for their software, so it is their responsibility. If they cannot react on a public holiday, tough luck. Just look at their payment terms. Do they want their money within 30 days or 25 work days? Usually it is the former, they don't care about your holidays, so why should anyone care about theirs? Also, the bad guys don't care about their victims' holidays. You are just giving them extra time to exploit. The only valid argument would be that the victims might not be reading the news about your disclosure on a holiday. But since you are again arguing about software used by a lot of companies (as opposed to private users), I don't see a problem there. They also have their guards on duty and their maintenance staff on call for a broken pipe or something.
What's most important is that I'm saying we should revert the "benefit of the doubt". A vast majority of corporations have shitty security handling. Even the likes of Google talk big with their 90 day time window from private irresponsible disclosure to public disclosure. And even Google regularly fails to fix things within those 90 days. So the default must be immediate public and full disclosure. Only when companies have proven their worth by correctly reacting to a number of those, then they can be given the "benefit of the doubt" and a heads up.
Because otherwise, when the default is irresponsible private disclosure, they will never have any incentive to get better. Their users will always be in danger unknowingly. The market will not have information to decide whether to continue buying from them. The situation will only get worse.